Update app.py

app.py

@@ -492,7 +492,7 @@ def apply_mask(d, b):
     if ksize/2 - int(ksize/2) == 0:
         ksize = ksize + 1
         
-    frame = cv2.imread(frames[frame_selected]).astype(np.uint8)
+    frame = cv2.imread(frames[frame_selected], cv2.IMREAD_UNCHANGED).astype(np.uint8)
     dmask = cv2.GaussianBlur(dmask, (ksize,ksize), 0)
     frame[:, :, 3] = 255 - dmask
     cv2.imwrite(frames[frame_selected], frame)